event-sourcing-cqrs的model有哪些

这篇文章主要介绍"event-sourcing-cqrs的model有哪些"，在日常操作中，相信很多人在event-sourcing-cqrs的model有哪些问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答"event-sourcing-cqrs的model有哪些"的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

Event

public abstract class Event {  private final UUID aggregateId;  private final ZonedDateTime timestamp;  private final int version;  protected Event(UUID aggregateId, ZonedDateTime timestamp, int version) {    this.aggregateId = checkNotNull(aggregateId);    this.timestamp = checkNotNull(timestamp);    this.version = version;  }  public UUID getAggregateId() {    return aggregateId;  }  public ZonedDateTime getTimestamp() {    return this.timestamp;  }  public int getVersion() {    return version;  }}

Event定义了aggregateId、timestamp、version属性

EventStore

public interface EventStore {  void store(UUID aggregateId, List newEvents, int baseVersion)      throws OptimisticLockingException;  List load(UUID aggregateId);}

EventStore接口定义了store、load方法

Aggregate

public abstract class Aggregate {  private UUID id;  private int baseVersion;  private List newEvents;  protected Aggregate(UUID id) {    this(id, emptyList());  }  protected Aggregate(UUID id, List eventStream) {    checkNotNull(id);    checkNotNull(eventStream);    this.id = id;    eventStream.forEach(e -> {      apply(e);      this.baseVersion = e.getVersion();    });    this.newEvents = new ArrayList<>();  }  protected void applyNewEvent(Event event) {    checkArgument(event.getVersion() == getNextVersion(),        "New event version '%s' does not match expected next version '%s'",        event.getVersion(), getNextVersion());    apply(event);    newEvents.add(event);  }  private void apply(Event event) {    try {      Method method = this.getClass().getDeclaredMethod("apply", event.getClass());      method.setAccessible(true);      method.invoke(this, event);    } catch (InvocationTargetException e) {      Throwables.propagate(e.getCause());    } catch (NoSuchMethodException | IllegalAccessException e) {      throw new UnsupportedOperationException(          format("Aggregate '%s' doesn't apply event type '%s'", this.getClass(), event.getClass()),          e);    }  }  public UUID getId() {    return id;  }  public int getBaseVersion() {    return baseVersion;  }  public List getNewEvents() {    return ImmutableList.copyOf(newEvents);  }  protected int getNextVersion() {    return baseVersion + newEvents.size() + 1;  }}

Aggregate定义了id、baseVersion、newEvents属性；其applyNewEvent方法会执行apply(event)及newEvents.add(event)；apply方法通过反射执行event的apply方法

ValueObject

public abstract class ValueObject {  @Override  public boolean equals(Object o) {    return EqualsBuilder.reflectionEquals(this, o);  }  @Override  public int hashCode() {    return HashCodeBuilder.reflectionHashCode(this);  }  @Override  public String toString() {    return ToStringBuilder.reflectionToString(this, ToStringStyle.SHORT_PREFIX_STYLE);  }}

ValueObject覆盖了equals、hashCode、toString方法

Specification

public interface Specification {  boolean isSatisfiedBy(T value);}

Specification接口定义了isSatisfiedBy方法

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